Liquid crystal device and liquid crystal apparatus

Abstract

A liquid crystal device is constituted by a pair of electrode plates and a liquid crystal composition disposed between the electrode plates. At least one of the electrode plates comprises a light-transmissive substrate, a plurality of electrodes including principal electrodes and auxiliary electrodes supported on the light-transmissive substrate, and an insulating layer. Each auxiliary electrode is disposed between an associated principal electrode and the light-transmissive substrate so as to be electrically connected with at least a part of the associated principal electrode, and the auxiliary electrodes being disposed with spacings therebetween which are filled with the insulating layer. The liquid crystal composition comprises at least one species of a fluorine-containing mesomorphic compound comprising a fluorocarbon terminal portion and a hydrocarbon terminal portion, the terminal portions being connected with a central core, and having smectic mesophase or latent smectic mesophase. The combination of the above specific cell structure and the specific liquid crystal composition is effective in improving display quality (e.g., contrast) while minimizing a voltage waveform deformation.

Description

FIELD OF THE INVENTION AND RELATED ARTThe present invention relates to a liquid crystal device used as, e.g., terminal displays for computers, various flat panel displays for word processors, typewriters and television receivers, view finders for video cameras, light valves for projectors, and light valves for liquid crystal printers. The present invention also relates to a liquid crystal apparatus using the liquid crystal device.The most popular and extensively used display may be CRTs (cathode ray tubes) which have been widely used for displaying motion (moving) pictures of television and video tape recorders or as monitor displays for personal computers. Based on the operation characteristic, the CRT is accompanied with difficulties such that the recognizability of a static image is lowered due to flickering and scanning fringes caused by an insufficient resolution, and the fluorescent member is deteriorated due to burning. Further, it has been recently found that electromagnetic...

AI Technical Summary

Benefits of technology

Particularly, when such a chiral smectic liquid crystal composition shows a larger spontaneous polarization of at least 10 nC / cm.sup.2, the resultant liquid crystal device (or apparatus) may suitably be used since the device provides more advantageous effects as described hereinbelow.

The liquid crystal composition used in the present invention may further contain other compounds and additives, such as another mesomorphic compound, an antioxidant, an ultraviolet ray-absorbing agent, a dye and a pigment, as desired.

Hereinbelow, an embodiment of a process for producing the liquid crystal device according to the present invention as shown in FIG. 1 will be described with reference to FIGS. 2A-2E and FIGS. 3A-3F.

FIGS. 2A-2E shows a series of steps generally involved in a process for producing the (upper) electrode plate including the light-transmissive substrate 1a shown in FIG. 1, and FIGS. 3A-3F shows a series of steps generally involved in a process for producing the (lower) electrode plate including the light-transmissive substrate 1b.

Referring to FIG. 2A, a plurality of metal electrodes (as auxiliary electrodes) 3a are formed on a light-transmissive substrate (e.g., glass substrate) la by forming a metal layer thereon, followed by patterning of the metal layer.

More specifically, the metal layer can be formed by a known film-forming process, such as vacuum vapor deposition, electron beam deposition, ion plating, chemical vapor deposition (CVD) or sputtering, depending on the metal species used. Further, the patterning of the metal layer can also be performed by, e.g., etching or photolithographic process, depending on the metal species used and / or a production process adopted.

Problems solved by technology

Based on the operation characteristic, the CRT is accompanied with difficulties such that the recognizability of a static image is lowered due to flickering and scanning fringes caused by an insufficient resolution, and the fluorescent member is deteriorated due to burning.

Further, it has been recently found that electromagnetic wave emitted from CRTs can adversely affect human bodies and health of VDT (video display terminal) operators.

Further, the CRT structurally has a large rearward space behind the display surface, so that the space economization in offices and at home may be obstructed thereby.

This type of liquid crystal device is however accompanied with a problem that it is liable to cause crosstalk when driven in a multiplex manner by using an electrode matrix of a high pixel density, and therefore the number of pixels is restricted.

As a result, the problems of crosstalk and response speed can be solved but, on the other hand, a larger area device of the type poses an extreme difficulty in industrial production thereof without inferior pixels.

Further, even if such production is possible, the production cost can be increased enormously.

Such a chiral smectic liquid crystal is accompanied with problems, such as the occurrence of zigzag-shaped alignment defects and twisting of liquid crystal molecules between a pair of substrates (called "splay alignment") leading to a lowering in contrast (as described in, e.g., "Structures and Properties of Ferroelectric Liquid Crystals" authored by Atsuo Fukuda and Hideo Takezoe; Corona Sha Publishing Co. Ltd., (1990)).

Another method is to apply an external electric field to a liquid crystal device containing a liquid crystal in a chevron structure to induce a bookshelf structure, but the resultant structure is rather unstable against an external stimulation, such as a temperature fluctuation.

However, such a liquid crystal material does not generally assume cholesteric phase, thus being liable to fail in providing a sufficiently good alignment state.

If the light transmittance of the transparent electrodes, etc. is low, a resultant contrast is undesirably lowered since the liquid crystal device is used as, e.g., displays or optical shutters by controlling the light transmittance.

Accordingly, a problem of voltage waveform deformation (distortion) due to electrical signal delay with respect to the transparent electrodes cannot be neglected.

In order to reduce the resistivity, it may be possible to increase the thickness of the transparent electrodes, but the formation of such thick transparent electrodes is not practicable due to a lowering in light transmittance.

As a result, such transparent electrodes having a high resistivity have caused a problem of voltage waveform deformation due to electrical signal delay along with increases in size and resolution of an effective optical modulation region (or display region) of the liquid crystal device.

Particularly, a surface-stabilized ferroelectric liquid crystal device (SSFLCD), such as a chiral smectic liquid crystal device, having a small cell thickness of 1-3 .mu.m, which is 1 / 314 1 / 5 of that of the conventional TN-type liquid crystal device, has encountered a problem of a larger voltage waveform deformation even when the SSFLCD employs electrode plates identical to those of the TN-type liquid crystal device.

However, the above practice (the formation of metal electrodes) have still left such problems that the thickness of the resultant metal electrodes cannot be made large since the cell thickness (or the thickness of a liquid crystal layer) is limited and that a boundary between an electrode plate and a liquid crystal becomes uneven due to the formation of the metal electrodes thereby to cause alignment defects.

These problems become more noticeable in the chiral smectic liquid crystal device having a clear smectic layer structure.

Particularly, a liquid crystal device using a liquid crystal composition containing a fluorine-containing liquid crystal (mesomorphic) compound assuming no cholesteric phase is liable to fail to effect satisfactory optical modulation due to an occurrence of alignment defects.

Further when such a liquid crystal composition is used for displaying motion pictures, the metal electrodes have not been readily made thick to the extent that display failure due to the voltage waveform distortion can be remedied.

However, a large bias ratio corresponds to a large amplitude of a data signal and leads to an increase in flickering and a lower contrast, thus being undesirable in respect of image quality.

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